Compensatory investment in zebra finches: females lay larger eggs when paired to sexually unattractive males

Abstract

The classical version of the differential allocation hypothesis states that, when females reproduce over their lifetime with partners that differ in their genetic quality, they should invest more in reproduction with highquality males. However, in species with lifetime monogamy, such as the zebra finch, partner quality will typically remain the same. In this case, the compensatory investment (CI ) hypothesis predicts higher investment for low-quality males, because low genetic quality offspring are more dependent on maternal resources. Here, we show that female zebra finches invested more resources, both in terms of egg volume and yolk carotenoid content, when paired to a low genetic quality male, as judged from his previous ability to obtain extra-pair paternity in aviary colonies. We also found that females deposited slightly larger amounts of testosterone into eggs when paired to a low parental quality male, as judging from his previous success in rearing offspring. This is, to our knowledge, the first experimental support for the CI hypothesis in a species with lifetime monogamy. We stress that in more promiscuous species, the benefits of classical differential allocation may partly be neutralized by the supposed benefits of CI.

Strategic female reproductive investment in response to male attractiveness in birds

“…Thus, female birds show substantial flexibility in their reproductive investment across contexts, both in terms of egg production and parental care. Despite some studies with results in the opposite direction [25,26,55], this overall result provides strong evidence in favour of the theoretical prediction that females generally should invest more into reproduction when mated with high-quality males, and that increased investment for low-quality or non-preferred males should only be favoured under restricted circumstances likely to be rare within and among species [4,18]. Importantly, greater investment in terms of egg size or feeding rate when paired with attractive males implies that studies that do not estimate or control for maternal investment will tend to overestimate the direct and indirect benefits of male attractiveness (e.g.…”

Differential allocation in relation to mate song quality in the Bengalese finch

“…Because offspring viability was lower when females were forced to breed with non-preferred males, females compensated for this by increasing clutch size or egg mass (e.g. Bluhm & Gowaty 2004, Bolund et al 2009). Even though the majority of studies so far supported the differential allocation hypothesis rather than the compensation hypothesis especially in birds, the direction of differential allocation can be either positive or negative depending on species ecology or experimental setups (Harris & Uller 2009;Ratikainen & Kokko, 2010).…”

Reproductive compensation in broad-nosed pipefish females

“…Possible constraints to mate choice may be environmental, such as risk of predation (Booksmythe et al 2008) and limitations to dispersal (Byers et al 2005) or mate availability, or they may be social, such as in intra-sexual competition (Villanelli & Gherardi 1998) and sexual conflict (Shine et al 2004). Although both theories have been in the literature for at least a decade, only recently has the first attempt to model under which conditions each allocation strategy should be optimal (Harris & Uller 2009), and careful consideration of the prerequisites necessary for reproductive compensation to occur (Gowaty 2008;Bolund et al 2009) been published.…”